Answer:
The temperature required is near about 3 million kelvin
Explanation:
The brilliance of the star results from the nuclear reaction that take place in the core of the star and radiate a huge amount of thermal energy resulting from the fusion of hydrogen into helium.
For this reaction to take place, the temperature of the star's core must be near about 3 million kelvin.
The hydrogen atoms collide and starts and the energy from the collision results in the heating of the gas cloud. As the temperature comes to near about 
, the nuclear fusion reaction takes place in the core of the gas cloud.
The huge amount of thermal energy from the nuclear reaction gives the gas cloud a brilliance resulting in a protostar.
Answer:
5.71428571422 m/s
Explanation:
u = Initial velocity = 20 m/s
v = Final velocity
s = Displacement
a = Acceleration
Time taken = 15-1 = 14 s
Distance traveled in 1 second = 
The speed as she reaches the light at the instant it turns green is 5.71428571422 m/s
A) 750 m
First of all, let's find the wavelength of the microwave. We have
is the frequency
is the speed of light
So the wavelength of the beam is
Now we can use the formula of the single-slit diffraction to find the radius of aperture of the beam:
where
m = 1 since we are interested only in the central fringe
D = 30 km = 30,000 m
a = 2.0 m is the aperture of the antenna (which corresponds to the width of the slit)
Substituting, we find
and so, the diameter is
B) 0.23 W/m^2
First we calculate the area of the surface of the microwave at a distance of 30 km. Since the diameter of the circle is 750 m, the radius is
So the area is
And since the power is
The average intensity is
